聚焦离子束技术制造金刚石切削刀具的研究

概述了基于聚焦离子束（Focused Ion Beam,FIB）加工技术制备金刚石切削刀具的相关研究进展,并介绍了金刚石刀具在超精密加工领域的研究背景及其制造现状。作为一种先进的微纳制造技术,聚焦离子束已在微尺度金刚石刀具制造研究中发挥了重要作用。针对金刚石刀具的刃口半径、刃形精度等核心参数,国内外相关研究者开展了聚焦离子束制造方法与工艺优化研究,实现了高质量刀具的制造,聚焦离子束加工可获得刃口半径为15～22nm的金刚石刀具制造。从微观切削基础和微纳光学元件制造两个角度,论述了聚焦离子束制造金刚石刀具的应用研究进展,介绍了其在纳米切削机理、微纳尺度光学元件制造中的应用。最后从提高FIB制造效率、应用研究拓展等角度,对该领域未来的发展进行了展望。     

金刚石刀具刃口的动态微观机械强度各向异性评价方法

为了评价金刚石刀具刃口动态微观机械强度的各向异性,对金刚石晶体的动态微观机械强度进行了理论建模,包括抗拉、剪切和抗压强度.通过比较分析动态微观机械强度的各向异性分布特征,提出了基于金刚石晶体动态微观抗拉强度的刀具刃口微观机械强度各向异性评价新方法,即刀具刃口强度评价因子.刀具刃口强度评价因子越高,其对应的刀具刃磨质量或刀具耐用度就越好.最后,分别采用刃磨工艺实验和刀具耐用度实验对刃口强度评价因子的评价适用性进行了验证,实验数据和理论分析结果具有很好的一致性.     

评价金刚石刀具各向异性的周期键链模型

金刚石刀具机械研磨时会表现出很强的各向异性,因此寻找合适的模型来定量地描述该各向异性成为亟待解决的问题.通过深入分析金刚石刀具机械研磨的材料去除机理,使用周期键链(PBC)理论建立了定量描述金刚石刀具机械研磨各向异性的PBC模型.然后使用该模型对金刚石晶体的典型单形进行了晶面及其"好磨"和"难磨"方向的判定.在圆弧刃金刚石刀具研磨机上对{100}和{110}晶面进行了研磨实验,{110}晶面沿<100>方向研磨时最大塑性沟槽深度为19.8 nm,<110>方向为5.1 nm;{100}晶面<100>方向为9.8 nm,<110>方向为3.5 nm,与PBC模型的结论完全一致.最后,根据该模型和金刚石刀具使用中的磨损情况得到了优选的刀具晶面组合:前刀面和后刀面均选用{110}晶面.该PBC模型将为金刚石刀具的机械研磨提供有力的技术支持.     

铝基碳化硅精密铣削刀具磨损实验研究

针对铝基碳化硅切削加工中刀具易磨损、寿命低、切削难度大和加工成本高等问题,选用不同材料的硬质合金铣刀及金刚石铣刀进行切削加工实验,并利用扫描电镜和工具显微镜对高体积分数铝基碳化硅铣削时刀具磨损形态进行了分析研究.研究表明:硬质合金刀具前刀面和刃口磨损主要形式为粘结磨损和微崩刃,后刀面磨损主要为刻划磨损,而金刚石铣刀加工时刀具磨损很小;YG6X铣刀材料微观组织致密,抗磨损能力较强,宜粗加工时选用;金刚石刀体的硬度远大于SiC颗粒,且金刚石与工件的摩擦系数小,金刚石铣刀寿命远大于硬质合金铣刀,宜精加工时选用.     

面向石墨模具精密加工的金刚石涂层结构及性能

金刚石涂层具有接近天然金刚石的超高硬度及耐磨性,被认为是精密加工石墨模具的理想刀具涂层材料.金刚石涂层与刀具基体间的结合力及涂层表面状态是高速干式切削加工质量及效率的关键,金刚石涂层前处理过程控制及涂层工艺是影响金刚石涂层刀具综合性能的重要因素.本工作基于热丝化学气相沉积技术,采用酸-碱-酸三步法对硬质合金材料进行前处理,在涂层沉积过程中采用大气流量及高炉压沉积工艺在刀具基体表面沉积金刚石涂层.采用扫描电镜(SEM)、原子力显微镜(AFM)、拉曼光谱(Raman)、X射线衍射光谱(XRD)对涂层微观结构及物相结构进行分析表征,利用纳米压痕仪对金刚石涂层硬度进行测试,利用喷砂试验测试金刚石涂层的抗冲刷性能,利 用石墨模具切削试验表征金刚石涂层刀具的切削性能.结果表明,金刚石涂层呈典型八面体结构,涂层与基体紧密结合、无明显孔隙,金刚石涂层刀具表面粗糙度为157 nm,sp3键含量大于98％,(涂层硬度大于90 GPa),涂层沿(111)面择优生长,抗冲刷时间大于150 s(0.5 MPa,120目),涂层刀具高速切削石墨模具2 h后,被加工面表面粗糙度小于1 μm,达到进口刀具水平.切削完成后刀具前刀面出现少量崩缺,前刀面磨损是此类刀具加工石墨模具的主要磨损形式.     

基于CVD厚膜金刚石刀具的超声振动切削模具钢实验

采用化学气相沉积（chemicalvapordeposition,CVD）厚膜金刚石刀具进行模具钢超声振动切削实验．首先阐述刀具的材质特点,观测其刀尖微观形貌和切削刃截面轮廓．然后搭建了适应精密／超精密加工需求的超声振动切削实验装置,其中激振机构可稳定实现频率42．0kHz、振幅峰峰值8～9μm的振动输出．通过切削无氧铜实验证明该超声振动切削装置工作有效、稳定后,选用AISI420模具钢进行切削实验,研究切削工艺条件及切削用量对加工质量的影响,得到适用于CVD厚膜金刚石刀具的切削用量选取范围,对比研究发现超声振动切削在提升加工表面质量、减少金刚石刀具磨损方面均优于常规切削．本研究可使切削模具钢时的金刚石刀具磨损VBmax由500～600μm减少至40μm,模具铜表面粗糙度Ra由0．93μm改善至0．09μm．本研究为金刚石刀具超声振动切削模具钢的实用化积累工艺经验,并探索提供可行的技术实现途径．     

以铣代磨在冲击试样加工中的应用

介绍了笔者单位在冲击试样加工中应用基于高速切削加工技术的以铣代磨加工技术,代替了传统工艺中平面磨床的功能,改变了传统的冲击试样加工工艺。与磨削相比,以铣代磨切削力小,切削热影响小,刀具、试样变形小,实现了高精度、低粗糙度加工;同时单位时间材料切除率是磨床磨削的3~6倍,极大的提高了冲击试样的加工效率。     

WC-Co硬质合金/CVD金刚石涂层刀具研究现状

化学气相沉积(Chemical vapor deposition,CVD)金刚石涂层刀具具有高硬度、优异的耐磨性、良好的冲击韧性和化学稳定性,能满足高效率、高精度的加工要求,逐渐成为切削铝和高硅铝合金、碳纤维增强复合材料及石墨等轻质量高强度难加工材料的主流涂层刀具。基于WC-Co硬质合金为基体的CVD金刚石涂层刀具在切削加工过程中容易发生CVD金刚石涂层的剥落,自主研发结合性能优良、长时间加工稳定的WC-Co硬质合金/CVD金刚石涂层刀具仍是该领域国内外发展的必然趋势。目前,研究者为了提高WC-Co硬质合金/CVD金刚石涂层刀具的结合性能,采用化学刻蚀法和机械处理法相结合去除WC-Co硬质合金基体表层中的Co粘结相,发现其能增强涂层与基体的结合强度,但基体表层Co粘结相含量的减少容易导致基体中形成脆化层,降低基体的强度和韧性。为了减少基体的强度和韧性损失,研究者在WC-Co硬质合金基体和金刚石涂层之间制备稳定的含Co中间化合物或沉积中间层,成功阻挡Co粘结相的热扩散。除了上述方法外,研究者还通过调控金刚石涂层工艺参数和结构,将微米晶与纳米晶金刚石层叠相结合,来提高金刚石涂层刀具的摩擦学...     

热丝CVD法制备金刚石涂层刀具的研究现状

金刚石涂层刀具具有优异的硬度、耐磨性及导热性,在军事、航空航天等高精尖应用领域加工石墨、高硅铝合金、碳纤维增强塑料等难切削材料时无可替代,但目前金刚石涂层刀具存在两个问题:一是涂层与刀具间膜基结合力较差,导致涂层在使用中过早脱落;二是涂层表面粗糙度较大,难以保证被加工面的平整度与尺寸精度。本文从增强涂层结合力与降低涂层粗糙度两方面,将近年来科研人员对HFCVD法制备金刚石涂层的研究成果加以综述,并分析了各种因素对金刚石涂层刀具性能的影响。     

切削加工中振动产生的原因及消减措施

论述机械切削加工中振动现象及产生的原因,并从工件装夹、刀具刃磨、机床调整、切削用量选择等多方面提出相应的消除或减小振动的措施,进而避免切削加工中振动带来的负面影响。     

Anisotropic mechanical amorphization drives wear in diamond

Diamond is the hardest material on Earth. Nevertheless, polishing diamond is possible with a process that has remained unaltered for centuries and is still used for jewellery and coatings: the diamond is pressed against a rotating disc with embedded diamond grit. When polishing polycrystalline diamond, surface topographies become non-uniform because wear rates depend on crystal orientations. This anisotropy is not fully understood and impedes diamond's widespread use in applications that require planar polycrystalline films, ranging from cutting tools to confinement fusion. Here, we use molecular dynamics to show that polished diamond undergoes an sp(3)-sp(2) order-disorder transition resulting in an amorphous adlayer with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. Similarly to other planarization processes, the diamond surface is chemically activated by mechanical means. Final removal of the amorphous interlayer proceeds either mechanically or through etching by ambient oxygen.     

Study on Electro Discharge Diamond Wheel Grinding (EDGM) of Ceramic Materials

This paper focuses on studying the principal of machining of ceramic materials using diamond wheel grinding and electro-discharge machining (EDM) and hence a new machining method, diamond wheel grinding with electro-discharge machining (EDGM) was proposed. This combined machining technology merges the respective advantages from diamond wheel grinding and electro-discharge machining. It can, therefore, increase the efficiency and the quality of ceramics machining. Experimental results showed that the machining efficiency of the combined machining technique is two to three times of diamond wheel grinding with the same quality surface finish.     

The characteristics of machined surface controlled by multi tip arrayed tool and high speed spindle

In this study, we propose one of the ultra-precision machining methods that can be adapted brittle material as well as soft material by using multi arrayed diamond tips and high speed spindle. Conventional machining method is too hard to control surface roughness and surface texture against brittle material because particles of grinding tools are irregular size and material can be fragile. Therefore we were able to design tool paths and machine controlled pattern on surface by multi arrayed diamond tips which has uniform size made in MEMS fabrication and high speed spindle of which maximum speed is about 300,000 rpm. We defined several parameters that can have effect on machining surface. Those are multi array of diamond tips (n * n), speed of the air spindle, and feeding rate. Surface roughness and surface texture can be controlled by those parameters for micro machining.     

CBN grain wear and its effects on material removal during grinding of FGH96 powder metallurgy superalloy

Grinding with cubic boron nitride (CBN) superabrasive is a widely used method of machining superalloy in aerospace industries. However, there are some issues, such as poor grinding quality and severe tool wear, in grinding of powder metallurgy superalloy FGH96. In addition, abrasive wheel wear is the significant factor that hinders the further application of CBN abrasive wheels. In this case, the experiment of grinding FGH96 with single CBN abrasive grain using different parameters was carried out. The wear characteristics of CBN abrasive grain were analyzed by experiment and simulation. The material removal behavior affected by CBN abrasive wear was also studied by discussing the pile-up ratio during grinding process. It shows that morphological characteristics of CBN abrasive grain and grinding infeed direction affect the CBN abrasive wear seriously by simulation analysis. Attrition wear, micro break, and macro fracture had an important impact on material removal characteristics. Besides, compared with the single cutting edge, higher pile-up ratio was obtained by multiple cutting edges, which reduced the removal efficiency of the material. Therefore, weakening multiple cutting edge grinding on abrasive grains in the industrial production, such as applying suitable dressing strategy, is an available method to improve the grinding quality and efficiency. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00412-2     

Effect of activators on the properties of nickel coated diamond composite powders

Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm~(-3) or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with(111) plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.     

二维超声振动辅助化学机械磨削技术及单晶硅实验

为了提高材料去除率和加工通用性,本文提出了工具施加二维超声波振动辅助的化学机械磨削(CMG)复合加工方式,开发具有伸缩和弯曲两种模态的二维超声波振动子及实验装置.以单晶硅片为加工对象,进行单点切削加工轨迹特性分析,并比较不同加工模式以及加工参数对表面粗糙度和材料去除率的影响.实验结果表明,二维超声辅助下的单点切削轨迹存在更多延性加工趋势.在同样普通机床精度条件下,随着时间的增加,二维超声辅助CMG表面粗糙度明显改善,达到纳米级.较无超声情况下二维超声波辅助CMG复合加工材料去除率提高约1倍,可获得最优表面粗糙度5 nm,一维径向超声辅助加工结果次之.     

Study of trimming damages of CFRP structures in function of the machining processes and their impact on the mechanical behavior

The main focus of this paper is to investigate the defects generated by different machining processes (namely burr tool machining, abrasive water jet machining ‘AWJM’ and abrasive diamond cutter ‘ADS’) and their impact on the mechanical behavior of CFRP in quasi-static (compression and inter-laminar shear) and tensile–tensile fatigue tests. The cutting conditions are selected so that different levels of degradation can be obtained. The machined surface is characterized using roughness measuring devices with and without contact and SEM observations. The results show that the defects generated during the trimming process with a cutting tool are fibers pull-out and resin degradation. These defects are mainly located in the layers with the fibers oriented at −45° and 90°. However, when using abrasive water jet and abrasive diamond processes, the defects generated have the form of streaks and are not dependent on the fiber orientation. Furthermore, the results of quasi-static tests performed on specimens machined by cutting tools show that AWJ specimens offer a better resistance in compression but the ADS samples offer higher inter-laminar-shear strengths. Moreover, the results of fatigue tests show that specimens machined with a burr tool offer higher endurance limit. Finally, it is concluded that the type and the mode of the mechanical loading (quasi-static fatigue) affect the mechanical response of CFRP and favor a given machining process.